alter increased Delete field to the table

 

 

stu(
id, name,age,addr,note
)

New field later age stu table;

alter table stu add column sex char(1) null comment '性别' after age;

ALTER TABLE status ADD id VARCHAR(100) DEFAULT '' COMMENT '学生Id' AFTER room;

alter add command to increase the fields of the table.

ALTER add Syntax: alter table table add other field types;

For example, in a table field MyClass added passtest, type int (4), the default value is 0:
   MySQL> Table ALTER MyClass the Add passtest int (. 4) default '0';

1) indexed
   mysql> alter table add index table index name (field name 1 [, field name 2 ...]);

例子： mysql> alter table employee add index emp_name (name);

2) Add the primary key index
    mysql> alter table table add primary key (field name);

例子： mysql> alter table employee add primary key(id);

3) a unique restriction plus index
   mysql> alter table add unique table index name (field name);

例子： mysql> alter table employee add unique emp_name2(cardnumber);

4) To delete an index
   mysql> alter table table name drop index index name;

例子： mysql>alter table employee drop index emp_name;

5) adding fields
    mysql> ALTER TABLE table_name ADD field_name field_type ;

6) modify the original field name and type
    mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

7) Delete field
    MySQL ALTER TABLE table_name DROP field_name;

Original link: https: //blog.csdn.net/u013063153/article/details/53304325